Assessing Structural Integrity of Small Thrusters Using Computational Methods

The structural reliability of small-scale bipropellant thrusters is critically influenced by transient thermomechanical loads arising during ignition and early operation. Conventional FEM analyses often rely on steady-state or time-discretized inputs from CFD, which fail to capture the continuous evolution of thermal boundary conditions. This study introduces a time-continuous CFD–FEM coupling framework, in which the unsteady combustion of propylene (C₃H₆) and nitrous oxide (N₂O) is simulated in three dimensions providing heat flux, shear stresses, and pressure within the thruster wall. An analytical decay law is used to apply the heat flux to the FEM model, accounting for its progressive reduction caused by wall heating. The thermo-mechanical response is evaluated using a temperature-dependent elastic–plastic von Mises criterion, revealing early-stage plastic strain localized at the nozzle throat. These results emphasize the importance of time-continuous thermal coupling for accurate damage prediction. The proposed methodology offers a computationally efficient and physically consistent framework for structural integrity assessment and supports the optimization of non-regeneratively cooled thrusters in space propulsion.